Recirculating-air warming blanket

ABSTRACT

A thermal device includes an inflatable non-perforated blanket, a conduit structure, and a recirculating assembly. The inflatable non-perforated blanket is configured to transport warm air internally. The conduit structure is configured to provide conduit to transport the warm air externally to the inflatable non-perforated blanket. The recirculating assembly is configured to inflate the inflatable non-perforated blanket with the warm air and: (1) to cause the warm air to flow from the first port to the second port in a first direction, and (2) to recirculate the warm air through the conduit structure to flow from the second port to the first port in the first direction. The inflatable non-perforated blanket includes first and second sheets. The first sheet faces ambient air and has a first thermal conductivity. The second sheet faces the subject body and has a second thermal conductivity higher than the first thermal conductivity.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a Continuation of U.S. application Ser. No.16/663,279, filed on Oct. 24, 2019, which is hereby incorporated byreference herein in its entirety.

BACKGROUND Technical Field

One disclosed aspect of the embodiments relates to a warming device. Inparticular, an embodiment is related to a perioperativerecirculating-air warming blanket.

Description of the Related Art

Perioperative care is the medical care for patients before, during, andafter surgery. It is usually provided to patients in hospitals, surgicalcenters, medical facilities, or doctors' offices. The care includes aperiod, called a perioperative period, during which the patient isprepared by health care professionals (e.g., hospital staff, nurses,physician assistants) in various aspects prior to, during, or after thesurgery. These aspects may be physical, emotional, or psychological.

Hypothermia, defined as the state where the patient's core temperaturefalls below 36° C., may be beneficial and detrimental. The potentialbenefits may include protection against the deleterious effects ofcerebral ischemia and malignant hyperthermia. The detrimental effectsmay include increased susceptibility to perioperative wound infection bycausing impaired immunity. Other adverse effects of hypothermia includeshivering, lowered resistance to infection, and prolonged duration ofdrug action. To reduce these adverse effects, several techniques ordevices to warm the patient have been developed with various degrees ofsuccess. These include cotton blankets, warm fluid infusion, and forcedair warming.

In forced air warming techniques, warming blankets or devices have beenavailable for several years. U.S. Pat. No. 6,524,332 issued to Augustineet al. discloses a thermal blanket with tubes having a large number ofapertures with varying hole density. One disadvantage of this techniqueis the release of warm air outside the blanket, which generates plumesthat enhance turbulent mixing and dispersion of squames in the operatingroom (OR). The squames may reach the wound location, leading toincreased probability of infection. A study conducted by X. He, S.Karra. P. Pakseresht, S. V. Apte, and S. Elghobashi (“Effect ofheated-air blanket on the dispersion of squames in an operating room,”Int. J. Numer Meth Biomed Engen. 2018;e2960.https://doi.org/10.1002/cnm.2960) indicates that the hot air from theblower in these devices and the resultant plumes are capable of liftingthe particles and transporting them to the side tables, above theoperating table, and the surgical site. U.S. Pat. No. 8,772,676 issuedto Augustine et al. discloses a heating blanket. The disadvantages ofthis technique include the complex post-use care and non-disposability.Other devices or techniques suffer disadvantages such as high powerconsumption, non-disposability, required support of patient's bodyweight when used as a mattress.

SUMMARY

One disclosed aspect of the embodiments is directed to a thermal devicethat provides warm air to a disposable warming blanket with low powerconsumption and uniform temperature distribution.

A thermal device includes an inflatable non-perforated blanket, aconduit structure, and a recirculating assembly. The inflatablenon-perforated blanket has first and second ports at first and secondregions, respectively, and is configured to transport warm airinternally. The conduit structure is configured to provide conduit totransport the warm air externally to the inflatable non-perforatedblanket. The recirculating assembly is configured to inflate theinflatable non-perforated blanket with the warm air and: (1) to causethe warm air to flow from the first port to the second port in a firstdirection through the first and second regions of the inflatablenon-perforated blanket, and (2) to recirculate the warm air through theconduit structure to flow from the second port to the first port in thefirst direction externally to the inflatable non-perforated blanket. Theinflatable non-perforated blanket is adapted to fit a subject body andincludes first and second sheets forming first and second groups oftubes arranged longitudinally. The first sheet faces ambient air and hasa first thermal conductivity. The second sheet faces the subject bodyand has a second thermal conductivity higher than the first thermalconductivity.

Further features of the disclosure will become apparent from thefollowing description of exemplary embodiments with reference to theattached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating a system in a typical perioperativeenvironment.

FIG. 2 is a diagram illustrating the system in a top view.

FIG. 3 is a diagram illustrating a recirculating thermal device.

FIG. 4 is a diagram illustrating an inflatable non-perforated blanket ina section view.

FIG. 5 is a diagram illustrating a recirculating assembly.

FIG. 6 is a diagram illustrating a controller.

FIG. 7 is a diagram illustrating a conduit structure.

FIG. 8 is a diagram illustrating a first embodiment of a reconfigurableconduit structure operating in a first direction.

FIG. 9 is a diagram illustrating a first embodiment of a reconfigurableconduit structure operating in a second direction.

FIG. 10 is a diagram illustrating a second embodiment of areconfigurable conduit structure operating in a first direction.

FIG. 11 is a diagram illustrating a second embodiment of areconfigurable conduit structure operating in a second direction.

DESCRIPTION OF THE EMBODIMENTS

A description is given of several embodiments. In each embodiment, anexample is described where the disclosure is applied to a perioperativerecirculating thermal device.

A thermal device is an apparatus that includes an inflatablenon-perforated blanket, a conduit structure, and a recirculatingassembly. The inflatable non-perforated blanket has first and secondports at first and second regions, respectively, and is configured totransport warm air internally. The conduit structure is configured toprovide conduit to transport the warm air externally to the inflatablenon-perforated blanket. The recirculating assembly is configured toinflate the inflatable non-perforated blanket with the warm air and: (1)to cause the warm air stream to flow from the first port to the secondport in a first direction through the first and second regions of theinflatable non-perforated blanket, and (2) to recirculate the warm airstream through the conduit structure to flow from the second port to thefirst port in the first direction externally to the inflatablenon-perforated blanket.

The thermal device further includes a controller to control flow of thewarm air stream. This may be performed by sending control signals tovarious air valves located inside the conduits in the conduit structure.The valves are opened or closed to direct the air stream to flow in apredetermined direction.

The recirculating assembly includes a heater to generate the warm air byheating the air and a blower to blow the warm air to the inflatablenon-perforated blanket. The recirculating assembly may further includeat least an environmental sensor which may be any one of a temperaturesensor, a pressure sensor, and a flow sensor. There may be multipleenvironmental sensors populated around the recirculating assembly or anyother suitable locations. In one embodiment, the controller controls theflow based on a measurement obtained from the environmental sensor.

The conduit structure includes an inlet valve to control flow from theambient air. In one embodiment, it further includes an inflow conduit totransport the warm air to the first port, an outflow conduit totransport the warm air from the second port to a recirculating port, anda recirculating conduit to transport the warm air from the recirculatingport to the recirculating assembly. The recirculating conduit has arecirculating valve to control flow of the warm air. Each of the inflowand outflow conduits is a flexible hose.

In one embodiment, the controller opens the inlet valve to draw theambient air to the recirculating assembly and closes the recirculatingvalve in an initialization period. It closes the inlet valve to stopdrawing the ambient air to the recirculating assembly after the initialperiod and opens the recirculating valve to draw the warm air from theoutflow conduit, through the recirculating conduit and to therecirculating assembly.

The conduit structure is reconfigurable by the controller to reverseflow of the warm air stream from the first direction to a seconddirection opposite to the first direction. The second direction is fromthe second port to the first port when the warm air stream flows throughthe inflatable non-perforated blanket and is from the first port to thesecond port when the warm air flows externally to the inflatablenon-perforated blanket.

The inflatable non-perforated blanket may have a variety of shapes toaccommodate the subject or the patient body, such as the upper body, thelower body, the entire body, or any part of the body.

The conduit structure may be reconfigurable by the controller in a cyclebased on at least one of a time parameter and an environmental parameterfrom the measurement obtained from the environmental sensor.

FIG. 1 is a diagram illustrating a system 100 in a typical perioperativeenvironment. The system 100 includes an operating table or bed 110, asubject 120, and a recirculating thermal device 130. The system 100 mayinclude more or less than the above elements.

The operating table or bed 110 is a means on which the subject 120 liesduring a perioperative period. This may be before the surgery(preoperative), during surgery (intraoperative), or after surgery(postoperative). In some embodiments, the operating table or bed 110 maybe any suitable means for the subject 120 to rest on regardless of hisor her surgical condition. The subject 120 is a patient who isundergoing a surgery or who is in need of being warmed due to his or herhealth conditions. The recirculating thermal device 130 provides warmthto the subject 120 using a forced air warming technique. Typically, amedical staff (e.g., a nurse) puts the inflatable blanket 132 on thesubject 120 such that the inflatable blanket 132 covers the subject 120in a body area or region that needs warming. For example, the inflatableblanket 132 may cover the front side of the upper part of the body ofthe subject 120.

Depending on the condition of the subject 120, the inflatable blanket132 may cover the subject 120 directly with direct contact, or through alayer such as a garment, hospital gown, or a sheet. The inflatableblanket 132 is made of flexible material that can fit the body of thesubject 120. In addition, the inflatable blanket 132 may be covered byanother layer such as a regular blanket or a bed sheet.

The thermal device 130 includes an inflatable non-perforated blanket132, a conduit structure 134, a recirculating assembly 136, and acontroller 138. For clarity, these components are shown separately. Inparticular, the inflatable non-perforated blanket 132 may bemanufactured to be separate from the other components so that it can bedisposed of when necessary. In one embodiment, more than one componentmay be integrated into a single component, or a component may be splitto occupy in more than one other component. For example, the controller138 and the recirculating assembly 136 may be integrated into a singlecomponent.

The inflatable non-perforated blanket 132 is a flexible structure thatis non-perforated and completely sealed so that the warm air cannot leakout to the ambient air. This is to avoid contamination or infection tothe patient as discussed above. The blanket 132 contains a number oftubular ducts or tubes that are initially collapsed to become flat. Whenwarm air is blown into these tubes, the tubes are inflated to apredetermined size or under a predetermined pressure or temperature.Since the lower surface of the blanket 132 is made of high thermalconductivity material and is in contact with the body of the subject120, the tubes act as a heat source that allows the thermal energy inthe warm air to be transferred to the body of the subject 120.

The conduit structure 134 is configured to provide conduit to transportthe warm air externally to the inflatable non-perforated blanket 132.The conduit structure 134 is attached to the blanket 132 and therecirculating assembly 136 to provide a recirculating air path for thewarm air, when exiting the blanket 132 at the exit end, to return to theblanket 132 at the entrance end. The conduit structure 134 may beconfigured to transport the warm air in one fixed direction. In anotherembodiment, it may be reconfigured to transport the warm air in a firstdirection for some time period and then transport the warm air in asecond direction opposite of the first direction. In this reconfigurablemode, the process may be repeated or cycled as long as necessary tomaintain balance in thermal distribution over the surface of the blanket132 or to reduce the thermal or mechanical stress on the blanket 132.

The recirculating assembly 136 performs two basic functions: blowing thewarm air through the blanket 132 and heating the air to a predeterminedtemperature and maintaining the air temperature at that predeterminedtemperature. It pumps the warm air through the blanket 132, inflates thetubes in the blanket 132, and causes the warm air to flow through theblanket 132 and to recirculate through the conduit structure 134. Thewarm air, therefore, forms a continuous loop of flow of air stream thatcirculates through the blanket 132. The heat from the warm air streamcirculating through the blanket 132 is transferred to the body of thesubject 120 during the air flow through the blanket 132.

FIG. 2 is a diagram illustrating the system 100 in a top view. As inFIG. 1 , the system 100 includes an operating table or bed 110, asubject 120, and a thermal device 130. As in FIG. 1 , the thermal device130 includes an inflatable non-perforated blanket 132, a conduitstructure 134, a recirculating assembly 136, and a controller 138. Fromthe top down, it is seen that the inflatable non-perforated blanket 132covers the upper part of the body of the subject 120. The recirculatingassembly 136 and the controller 138 are shown to be located under theoperating table or bed 110 for illustrative purposes. They can belocated or positioned at any suitable location.

FIG. 3 is a diagram illustrating a thermal device 130 with a detaileddescription of its components. As in FIGS. 1 and 2 , the thermal device130 includes the inflatable non-perforated blanket 132, the conduitstructure 134, the recirculating assembly 136, and the controller 138.FIG. 3 shows the details of the inflatable non-perforated blanket 132and the interactions of these components. These components are typicallyseparated from one another. Therefore, the thermal device 130 is easy tomaintain and highly portable. In addition, the inflatable non-perforatedblanket 132 is separate from the other components and therefore it isdisposable when necessary. Since the inflatable non-perforated blanket132 is typically used on patients more often than the other components,it may be susceptible to wear-out. Accordingly, the disposability is abenefit that allows the thermal device 130 to be used for longerperiods. The inflatable non-perforated blanket 132 may have a number ofpositioning straps 370 to secure the blanket to desired locations overthe subject or patient body 120. The positioning straps 370 may be madeby any suitable materials such as plastic with any convenient fasteningmechanism such as adhesive.

The inflatable non-perforated blanket 132 has first and second ports 324and 328 at first and second airflow regions 344 and 348, respectively.The first and second ports 324 and 328 provide the mechanical interfaceto allow the conduit structure 134 to be connected, coupled, attached,clamped, fastened, or joined to the blanket 132. The inflatablenon-perforated blanket 132 is configured to transport warm air 310internally. The first port 324 provides the connection to the conduitstructure 134 at one end for the warm air 310 to flow into the blanket132 (in a first direction 330), or to flow out of the blanket 132 in asecond direction 930 (shown in FIGS. 9 and 11 ) opposite of the firstdirection 330. The second port 328 provides the connection to theconduit structure 134 at another end for the warm air 310 to flow out ofthe blanket 132 (in a first direction 330), or to flow into the blanket132 in a second direction 930 (shown in FIGS. 9 and 11 ) opposite of thefirst direction 330.

The first and second airflow regions 344 and 348 are in contact withfirst and second tubular regions 354 and 358, respectively. The firstand second tubular regions 354 and 358 include several tubular ducts ortubes 384 and 388, respectively, arranged longitudinally or along thelength of the blanket 132.

Both the first and second tubular regions 354 and 358 are in contactwith a common airflow region 360 at the distal end. The first air flowregion 344 and the first tubular regions 354 are separated from (i.e.,not in contact with) the second air flow region 348 and the secondtubular regions 358 by a region separator 322. The region separator 322prevents the warm air flowing through the first airflow regions 344 andthe first tubular region 354 from leaking into the second airflowregions 348 and the second tubular region 358, and vice versa.

The warm air 310 flows through the inflatable non-perforated blanket 132in the first direction 330 due to the blowing force of the electricblower in the recirculating assembly 136. The first direction 330traverses the inflatable non-perforated blanket 132 from the first port324 at point A to point B at the end of the first airflow region 344.The warm air 310 then flows into the multiple tubes 384. The tubes 384transport the warm air from the first airflow region 344 (marked bypoints A and B) to the common airflow region 360 (marked by points C andD). In the common airflow region 360, there is no region separator.Therefore, the warm air stream 310 can flow freely from the regionmarked CD to the region marked EF. Then, the warm air stream 310continues flowing through the second tubular region 358. Specifically,the warm air stream 310 flows through the tubes 388 from the common airflow region 360 (marked by points E and F) to the second air flow region348 (marked by points G and H). The region separator 322 prevents thewarm air stream 310 from leaking or permeating to the first tubularregion 354. The warm air stream 310 then exits the inflatablenon-perforated blanket 132 through the second port 328 and enters theconduit structure 134 to recirculate back to the first port 324.

As discussed above, the conduit structure 134 is configured to provideconduit to transport the warm air stream externally to the blanket 132.The recirculating assembly is configured to inflate the inflatablenon-perforated blanket with the warm air and: (1) to cause the warm airstream 310 to flow from the first port 324 to the second port 328 in thefirst direction 330 through the first and second tubular regions 354 and358 of the blanket 132, and (2) to recirculate the warm air stream 310through the conduit structure 134 to flow from the second port 328 tothe first port 324 in the first direction 330 externally to theinflatable non-perforated blanket 132.

FIG. 4 is a diagram illustrating the inflatable non-perforated blanket132 in a section view. The inflatable non-perforated blanket 132 isadapted to fit the body of the subject 120. It may be attached ortightened to the subject 120 in any suitable manner, such as using theprovided self-adhesive plastic straps 370. It includes a first sheet 410and a second sheet 420. The first and second sheets 410 and 420 are madeof stretchable or flexible material such as plastic.

The first sheet 410 faces the ambient air or the external area and has afirst thermal conductivity which is very low (to act as an insulator).The second sheet 420 faces the body of the subject 120 and has a secondthermal conductivity. The second thermal conductivity is much higherthan the first thermal conductivity such that uniformity of temperaturedistribution when the warm air flows over the surface of the secondsheet is maintained.

In one embodiment, the first sheet 410 may be made of Polyvinyl chloride(PVC) which has a thermal conductivity coefficient of about 0.19 W/mK(Watts per meter-Kelvin), or epoxy which has a thermal conductivitycoefficient of about 0.17 W/mK, or any other suitable material. Thesecond sheet 420 may be made of any suitable material that issufficiently flexible. For example, the second sheet 420 may be made ofPolyethylene low density (PEL) which has a thermal conductivitycoefficient of about 0.33 W/mK, or Polyethylene high density (PEH) whichhas a thermal conductivity coefficient of about 0.5 W/mK. It may also bepossible to use advanced plastic materials that have much higher thermalconductivity coefficients, for example, in the order of 100 W/mK, tomake the second sheet 420.

The second sheet 420 is stretchable to accommodate the shape of thesubject 120. The first sheet 410 forms a layer on the second sheet 420and is press-sealed to the second sheet 420 at several tube segments430. The tube segments 430 are spaced at approximately equal distancesacross the width of the blanket 132 to define the tubes 384 and 388.Initially the sheet 410 is flat and the tubes 384 and 388 are in adeflated state. When air is pumped into the blanket 132, the warm airstream 310 inflates the tubes 384 and 388 as it travels along the lengthof the blanket 132.

The first sheet 410 is also press-sealed at the region separator 322 sothat it acts as a barrier to prevent the warm air stream 310 fromleaking or penetrating between the first and second tubular regions 354and 358. The region separator 322 stops at the common air flow region360 to allow the warm air 310 to flow from the first tubular regions 354to the second tubular regions 358 in the first direction 330 or from thesecond tubular regions 358 to the first tubular regions 354 in thesecond direction 930 (in FIG. 9 ).

FIG. 5 is a diagram illustrating the recirculating assembly 136. Therecirculating assembly 136 is configured to generate the warm air stream310 that inflates the inflatable non-perforated blanket 132. The forceprovided by the recirculating assembly 136 causes the warm air to flowthrough the blanket 132 internally and to recirculate through theconduit structure 134 externally to the blanket 132. The recirculatingassembly 136 includes a motor 512, a blower 514, and a heater 516. Ithas an inlet port 532 that receives the ambient air 315 during theinitialization period. It has an outlet port 534 to deliver the warm airstream 310 to the blanket 132 through the conduit structure 134. In someembodiments, it also has a recirculating port 536 to provide connectionto the recirculating air stream in a reconfigurable mode.

The motor 512 provides power to the blower 514. It may be an electricmotor that drives the blower 514 with a shaft. The blower 514 blows theair and creates a force that pushes or propels the air forward towardthe outlet port 534. The blower 514 may be any suitable blower. It mayinclude a propeller or several fan blades arranged with a wheel in anappropriate structural assembly. The blade and wheel mechanism may beany suitable configuration, such as shrouded radial blade, open radialblade, open paddle wheel, backward inclined, backward curved, airfoilblade, forward curved multi-vane (squirrel cage), and backward curvedradial.

The heater 516 may employ any suitable heating mechanism, such asresistive heating. The heater 516 may be remotely controlled by thecontroller. Once activated, it generates heat to warm the air streamblown by the blower 514. One particular advantage of an embodiment ofthe recirculating thermal device 130 is the efficient energyutilization. Since the warm air recirculates through the blanket 132,any amount of heat that is not fully transferred to the subject 120continues to flow through the recirculating assembly 136. Accordingly,except during the initialization period, the heater 516 does not heatfresh cool air from the ambient air 315. Instead, it heats an air streamthat has been heated before. Accordingly, the heater 516 does not needto provide a full heating power as in the initialization period. Itneeds only to provide enough heat to maintain the temperature of thewarm air stream at a predetermined level. The environmental sensors 570located in the recirculating assembly 136 or other locations include oneor more temperature sensors that provide readings of the air streamtemperature. Based on these readings, which may be obtained remotely,the controller 138 generates control signal to the heater 516 to adjustthe power accordingly.

The arrangement of the motor 512, the blower 514, and the heater 516 mayfollow any configuration that provides an efficient power utilizationand noise suppression. For example, the blower 514 may be positioned toblow the air toward the motor 512 and the heater 516 to provide acooling mechanism for the motor 513. Alternatively, the motor 512 may bepositioned outside the air stream to provide more air propulsionefficiency.

FIG. 6 is a diagram illustrating the controller 138. The controller 138is configured to control the flow of the warm air stream 310. Thecontroller 138 includes a processing device 610, a peripheral interface630, a memory device 620, a display 640, an I/O device 650, and acommunication device 660. These components may be located in a housingor scattered at several locations. The controller 138 may include moreor less components than the above. In addition, some components may beintegrated into a single component or split into more components.Furthermore, not all components are located or positioned within thesame housing. For example, the I/O device 650 (e.g., keyboard) may belocated outside the housing of the controller 138 to allow a user toenter control parameters or other information. Similarly, the display640 may be located outside the housing to allow a user to read thestatus of the thermal device.

The processing device, processor, or circuit 610 is a programmabledevice that may execute a program or a collection of instructions tocarry out a task. It may be a central processing unit (CPU), ageneral-purpose processor, a digital signal processor, amicrocontroller, or a specially designed processor such as one designfrom Applications Specific Integrated Circuit (ASIC).

The peripheral interface 630 in a highly integrated chipset thatincludes many functionalities to provide interface to several devicessuch as memory devices, input/output devices, storage devices, networkdevices, etc. The memory device 620 may be any appropriate memorydevices such as random access memory (RAM), read-only memory (ROM),cache memory, and flash memory. The memory device 620 may storeinstructions or programs, loaded from a mass storage device (e.g., amemory stick), that, when executed by the processing device 610, causethe processing device 610 to perform operations as described elsewhere,such as flow control. It may also store data used in the operations,including the control parameters, the predetermined levels orthresholds. The ROM may include instructions, programs, constants, ordata that are maintained whether it is powered or not. The flash memorymay store programs, instructions, constants, tables, coefficients. Itmay be erased and programmed as necessary.

The display 640 may include a display device such as liquid crystaldisplay (LCD), light-emitting diode (LED), etc. The display may providethe status of the thermal device, sensor readings, and other userinterface functionalities. The I/O device or controller 650 controlsinput devices (e.g., stylus, keyboard, mouse, microphone, sensors) andoutput devices (e.g., display, audio devices, speaker, scanner,printer). The communication device 660 provides interface to a networkand/or a wireless controller. The communication device 660 transmits andreceives information or data packets to and from a wired, wirelessnetwork (nor shown). It may receive readings from the environmentalsensors 570. It may also issue commands or control signals to theconduit structure 134, such as activating or deactivate the air valves.The network may be a local area network (LAN), an intranet, an extranet,or the Internet.

The Conduit Structure:

The thermal device 130 may operate in one or more operational modes.These modes include a fixed mode and a reconfigurable mode. In the fixedmode, the thermal device 130 operates with a simple structure andconfiguration where the direction of the air stream is fixed, forexample, the first direction 330. In the reconfigurable mode, thethermal device 130 operates with a complex structure and configurationwhere the direction of the air stream is changed between the firstdirection 330 and the second direction 930. The component that plays themain role in the mode configuration is the conduit structure 134.

FIG. 7 is a diagram illustrating the thermal device 130 using theconduit structure 134 in a fixed mode. The conduit structure 134includes the components outside the blanket 132 and the recirculatingassembly 136. It is shown in shaded area in the diagram. The conduitstructure 134 in the fixed mode includes an inflow conduit 712, anoutflow conduit 714, a recirculating conduit 716, an inlet valve 725 anda recirculating valve 727.

The inflow conduit 712 connects the recirculating assembly 136 to theblanket 132 at the first port 324. It may be any suitable conduit suchas a flexible or corrugated hose or tube. It transports the warm airstream 310 from the recirculating assembly 136 to the blanket 132. Theoutflow conduit 714 connects the blanket 132 to the recirculatingassembly 136 at the second port 328. It may be any suitable conduit suchas a flexible or corrugated hose or tube. It transports the warm airstream 310 from the blanket 132 to the recirculating assembly 136 to theblanket 132 via the recirculating conduit 714. The recirculating conduit714 provides a path for the warm air stream 310 to recirculate. Theinlet valve 725 controls the flow of the air stream from the ambient air315 to the recirculating assembly 136. The recirculating valve 727 islocated in the recirculating conduit 716 to control the flow of the airstream from the blanket 132 to the recirculating assembly 136. In oneembodiment, the inlet valve 725 and/or the recirculating valve 727operates in an on-off mode where the valve is open to allow the airstream to pass through or is closed to inhibit the air stream to passthrough. The mechanism to activate the opening or closure of the valvemay be performed by wired or wireless controls.

The operation of the conduit structure 134 is under the control of thecontroller 138. In essence, the controller 138 receives theenvironmental readings from one or more environmental sensors 570 andactivates or deactivates the valves 725 and 727 according to thesereadings. In addition, the controller 138 may perform operationsindependently of the environmental readings such as based on a timer oruser's inputs.

In a typical scenario, the thermal device in the fixed mode has twooperational periods: an initialization period and an operational period.In the initialization period, the recirculating assembly 136 draws theambient air 315 and blows the heated air to inflate the tubes 384 and388 inside the blanket 132 and propels the warm air through these tubes.The environmental sensor 570, such as a pressure sensor, monitors theair pressure at the inlet port 532 or outlet port 534, or the inflowand/or outflow conduits 712 and 714. It continuously transmits themeasured parameter to the controller 138 either through wired orwireless connections. When this pressure reaches a predetermined level,the thermal device 130 switches to the operational period. In theoperational period, the thermal device 130 stops drawing the ambient air315 and allows the warm air to recirculate.

The operation of the thermal device 130 may be carried out as follows.In the initialization period, the controller 138 closes therecirculating valve 727 and opens the inlet valve 725 to draw theambient air 315 to the recirculating assembly 136. From the ambient air315, it generates the warm air stream 310. The warm air stream 310 flowsfrom point Y at the outlet port 534 through the inflow conduit 712 tothe first port 324 at point A, and enters the blanket 132. The warm airstream 310 continues to flow in the first directions 330 to the commonair flow region 360 and to the second port 328 at point H. The warm airstream 310 then exits the blanket 132 and flows through the outflowconduit 714. Since the recirculating conduit 716 is closed at point Z,the warm air stream 310 cannot exit, allowing the air pressure insidethe blanket 132 to build up. Eventually, the air pressure inside theblanket 132 reaches a predetermined level, which indicates that thetubes 384 and 388 have been sufficiently inflated. At that point, thecontroller 138 sends the control signals to close the inlet valve 725and to open the recirculating valve 727 and the thermal device 130enters the operational period.

In the operational period, the recirculating assembly 136 stops drawingthe ambient air 315 to the recirculating assembly 136 and draws the warmair stream 310 from the outflow conduit 714 through the recirculatingconduit 716 and to the inlet port 532 of the recirculating assembly 136.The warm air stream 310 continuously recirculates in a closed loop thatflows through the blanket 132 and the recirculating assembly 136.

The conduit structure 134 may be designed to be reconfigurable so thatthe flow direction of the warm air stream may be reversed and cycledback and forth in any desired time period. By cycling the warm airstream in two opposite directions, the thermal device 130 reduces thethermal and/or mechanical stress on the surface of the sheets of theblanket 132 and accommodates any irregularities of the shape of thesubject 120 to balance the thermal distribution. Two embodimentsillustrate this reconfigurable mode. FIGS. 8 and 9 show the firstembodiment. FIGS. 10 and 11 show the second embodiment.

FIG. 8 is a diagram illustrating the thermal device 130 using a firstembodiment of a reconfigurable conduit structure 134 operating in afirst direction. The inflow conduit 712 is replaced by a first conduit802 and the outflow conduit 714 is replaced by a second conduit 804 toreflect the bidirectional nature of these conduits. In addition to therecirculating conduit 716 and the inlet conduit 722 shown in FIG. 7 ,the conduit structure 134 has an outlet conduit 836 and two branchconduits 832 and 834. It has several air valves to change the air streamdirection. For illustration, six valves are shown. The inlet valve 725is located at the inlet conduit 722 to draw the ambient air 315 and therecirculating valve 727 is located at the recirculating conduit 722 toprovide conduit for the recirculating air stream as before. The outletconduit 836 has a valve 822. The branch conduit 832 has a valve 812located near the inlet conduit 722 and a valve 824 located near theoutlet conduit 836. Depending on the size of the branch conduit 832, thetwo valves 812 and 824 may be merged into a single valve. The branchconduit 834 has a valve 816 near the recirculating conduit 714 and avalve 818 near the outlet conduit 836. Depending on the size of thebranch conduit 834, the two valves 816 and 818 may be merged into asingle valve.

In the initial period, the controller 138 controls the valves asfollows: closes the valves 727, 812, 824, 816, and 818; and opens thevalves 725 and 822. The ambient air 315 is drawn into the recirculatingassembly 136 through the inlet conduit 722. The warm air stream 310exits the recirculating assembly 136 and is propelled to enter theblanket 132 through the first conduit 802. The warm air stream 310 exitsthe blanket 132 and flows through the second conduit 804. Since thevalves 727 and 816 are closed the warm air stream 310 accumulates atpoint Z to build up pressure. When the internal pressure reaches apredetermined level, the initialization period is completed and thethermal device 130 switches to the operational period. This is performedby the controller 138 to control the valves by issuing control signalsto open or close the valves accordingly.

In the operational period, the thermal device 130 can direct the warmair stream 310 in two directions. FIG. 8 illustrates the first direction330 and FIG. 9 illustrates the second direction 930. As discussedearlier, the first direction 330 goes from the first port 324 (point Ain FIG. 7 ) to the second port 328 (point H), then from point H topoints Z and X, then through the recirculating assembly 136 to points Vand Y, and returns to point A. The controller 138 issues control signalsto the valves to direct the warm air stream to flow in the firstdirection 330 as follows: closes the valves 725, 812, 824, 816, 818; andopens the valves 727 and 822.

FIG. 9 is a diagram illustrating the thermal device 130 using a firstembodiment of a reconfigurable conduit structure 134 operating in asecond direction. FIG. 9 only illustrates the operational mode. Theinitialization mode is the same as in FIG. 8 . The second direction isshown as the arrow 930. The second direction 930 goes from the inletport 532 (point X) through the recirculating assembly 136 to points V;then from point V to point Z; then through the second conduit 804 to thesecond port 328 (point H); then through the blanket 132 to the firstport 324 (point A); then through the first conduit 802 to point Y; andthen from point Y to point X and continues through the recirculatingassembly 136.

The controller 138 issues control signals to the valves to direct thewarm air stream to flow in the second direction 930 as follows: closesthe valves 725, 727, and 822; and opens the valves 816, 818, 812, and824.

FIG. 10 is a diagram illustrating the thermal device 130 using a secondembodiment of a reconfigurable conduit structure 134 operating in afirst direction. The conduit structure 130 has the first and secondconduits 802 and 804 as in FIG. 8 . It has three conduits: the outletconduit 836 and three branch conduits 1002, 1004, and 1006. It has sixvalves. The inlet valve 725 is located at the inlet conduit 722 asbefore. The outlet conduit 836 has a valve 1018. The branch conduit 1002has valves 1014 and 1016. Depending on the size of the conduit 1002, thevalves 1014 and 1016 may be merged into a single valve. The branchconduit 1004 has a valve 1012. The branch conduit 1016 has a valve 1022.

In the initial period, the controller 138 controls the valves asfollows: closes the valves 1012, 1014, 1016, and 1022; and opens thevalves 725 and 1018. The ambient air 315 is drawn into the recirculatingassembly 136 through the inlet conduit 722. The warm air stream 310exits the recirculating assembly 136 and is propelled to enter theblanket 132 through the outlet conduit 836 and the first conduit 802.The warm air stream 310 exits the blanket 132 and flows through thesecond conduit 804. Since the valves 1012 and 1022 are closed, the airstream 310 accumulates at valve 1012 to build up pressure. When theinternal pressure reaches a predetermined level, the initializationperiod is completed and the thermal device 130 switches to theoperational period. As before, this is performed by the controller 138to control the valves.

In the operational period, the thermal device 130 can direct the warmair stream 310 in two directions. FIG. 10 illustrates the firstdirection 330 and FIG. 11 illustrates the second direction 930. Thefirst direction 330 goes from the first port 324 (point A) to the secondport 328 (point H), then from point H to points S and Q near valve 1012,then through the recirculating assembly 136 to point V and then to pointR near valve 1018, and returns to point A. The controller 138 issuescontrol signals to the valves to direct the warm air stream 310 to flowin the first direction 330 as follows: closes the valves 725, 1014,1016, and 1022; and opens the valves 1012 and 1018.

FIG. 11 is a diagram illustrating the thermal device 130 using a secondembodiment of a reconfigurable conduit structure 134 operating in asecond direction. FIG. 11 only illustrates the operational mode. Theinitialization mode is the same as in FIG. 10 . The second direction isshown as the arrow 930. The second direction 930 goes from the outletport 534 (point V) to point R and turns to point S; then from point Sthrough the second conduit 804 to the second port 328 (point H); throughthe blanket 132 to the first port 324 (point A); then through the firstconduit 802 to point T; and then from point T to point Q and continuesthrough the recirculating assembly 132.

The controller 138 issues control signals to the valves to direct thewarm air stream to flow in the second direction 930 as follows: closesthe valves 725, 1012, and 1018; and opens the valves 1014, 1016, and1022.

Variations of the above configurations may be carried out. For example,additional conduits or valves may be included to provide moreflexibility in directing the warm air stream.

Elements of one embodiment may be implemented by hardware, firmware,software or any combination thereof. The term hardware generally refersto an element having a physical structure such as electronic,electromagnetic, optical, electro-optical, mechanical,electro-mechanical parts, etc. A hardware implementation may includeanalog or digital circuits, devices, processors, applications specificintegrated circuits (ASICs), programmable logic devices (PLDs), fieldprogrammable gate arrays (FPGAs), or any electronic devices. The termsoftware generally refers to a logical structure, a method, a procedure,a program, a routine, a process, an algorithm, a formula, a function, anexpression, etc. The term firmware generally refers to a logicalstructure, a method, a procedure, a program, a routine, a process, analgorithm, a formula, a function, an expression, etc., that isimplemented or embodied in a hardware structure (e.g., flash memory,ROM, EROM). Examples of firmware may include microcode, writable controlstore, micro-programmed structure.

When implemented in software or firmware, the elements of an embodimentmay be the code segments to perform the necessary tasks. Thesoftware/firmware may include the actual code to carry out theoperations described in one embodiment, or code that emulates orsimulates the operations. The program or code segments may be stored ina processor or machine accessible medium. The “processor readable oraccessible medium” or “machine readable or accessible medium” mayinclude any non-transitory medium that may store information. Examplesof the processor readable or machine accessible medium that may storeinclude a storage medium, an electronic circuit, a semiconductor memorydevice, a read only memory (ROM), a flash memory, an erasableprogrammable ROM (EPROM), a floppy diskette, a compact disk (CD) ROM, anoptical disk, a hard disk, etc. The machine accessible medium may beembodied in an article of manufacture. The machine accessible medium mayinclude information or data that, when accessed by a machine, cause themachine to perform the operations or actions described above. Themachine accessible medium may also include program code, instruction orinstructions embedded therein. The program code may include machinereadable code, instruction or instructions to perform the operations oractions described above. The term “information” or “data” here refers toany type of information that is encoded for machine-readable purposes.Therefore, it may include program, code, data, file, etc.

All or part of an embodiment may be implemented by various meansdepending on applications according to particular features, functions.These means may include hardware, software, or firmware, or anycombination thereof. A hardware, software, or firmware element may haveseveral modules coupled to one another. A hardware module is coupled toanother module by mechanical, electrical, optical, electromagnetic orany physical connections. A software module is coupled to another moduleby a function, procedure, method, subprogram, or subroutine call, ajump, a link, a parameter, variable, and argument passing, a functionreturn, etc. A software module is coupled to another module to receivevariables, parameters, arguments, pointers, etc. and/or to generate orpass results, updated variables, pointers, etc. A firmware module iscoupled to another module by any combination of hardware and softwarecoupling methods above. A hardware, software, or firmware module may becoupled to any one of another hardware, software, or firmware module. Amodule may also be a software driver or interface to interact with theoperating system running on the platform. A module may also be ahardware driver to configure, set up, initialize, send and receive datato and from a hardware device. An apparatus may include any combinationof hardware, software, and firmware modules.

It will be appreciated that various of the above-disclosed and otherfeatures and functions, or alternatives thereof, may be desirablycombined into many other different systems or applications. Variouspresently unforeseen or unanticipated alternatives, modifications,variations, or improvements therein may be subsequently made by thoseskilled in the art which are also intended to be encompassed by thefollowing claims.

What is claimed is:
 1. An apparatus comprising: an inflatablenon-perforated blanket having first and second ports at first and secondregions, respectively, and configured to transport warm air internallyin a flow direction; a conduit structure configured to provide conduitto transport the warm air externally to the inflatable non-perforatedblanket in the flow direction; and a recirculating assembly configuredto inflate the inflatable non-perforated blanket with the warm air and:(1) to cause the warm air to flow in the flow direction internally tothe inflatable non-perforated blanket, and (2) to recirculate the warmair through the conduit structure to flow in the flow directionexternally to the inflatable non-perforated blanket; wherein theinflatable non-perforated blanket is adapted to fit a subject body andincludes first and second sheets forming first and second groups oftubes arranged longitudinally, wherein the first sheet faces ambient airand is made of a first material, wherein the second sheet faces thesubject body and is made of a second material different from the firstmaterial, and wherein the conduit structure has a reconfigurableoperational mode to operate in a first mode and a second mode so thatthe flow direction is reversible between a first direction in the firstmode and a second direction in the second mode.
 2. The apparatus ofclaim 1 wherein the first direction is from the first port to the secondport and the second direction is from the second port to the first port.3. The apparatus of claim 2 further comprising a controller to controlthe reconfigurable operational mode.
 4. The apparatus of claim 3 whereinthe recirculating assembly comprises: a heater to generate the warm airby heating; and a blower to blow the warm air to the inflatablenon-perforated blanket.
 5. The apparatus of claim 3 wherein the conduitstructure comprises an inlet valve to control flow from the ambient air.6. The apparatus of claim 5 wherein the conduit structure furthercomprises: a first conduit to transport the warm air to the first portin the first direction and to transport the warm air from the first portin the second direction; and a second conduit to transport the warm airfrom the second port in the first direction and to transport the warmair to the second port in the second direction; and a first branchconduit to transport the warm air from the first conduit to therecirculating assembly in the second direction, a second branch conduitto transport the warm air from the recirculating assembly to the secondconduit in the second direction, and a plurality of valves to controlthe operational mode, wherein in the first mode the first branch conduitand second branch conduit are closed to allow the warm air to flow fromthe second conduit to the first conduit through the recirculatingassembly, and wherein in the second mode the first branch conduit andsecond branch conduit are open to allow the warm air to flow from thefirst conduit to the second conduit through the recirculating assembly.7. The apparatus of claim 6 wherein one of the first and second conduitsis a flexible hose.
 8. The apparatus of claim 6 wherein the controller:opens the inlet valve to draw the ambient air to the recirculatingassembly and closes a recirculating valve in an initial period; andcloses the inlet valve to stop drawing the ambient air to therecirculating assembly after the initial period and opens therecirculating valve to draw the warm air from the first conduit or thesecond conduit, through a recirculating conduit and to the recirculatingassembly.
 9. The apparatus of claim 5 wherein the first material has afirst thermal conductivity and the second material has a second thermalconductivity higher than the first thermal conductivity.
 10. Theapparatus of claim 6 wherein the recirculating assembly includes anenvironmental sensor being one of a temperature sensor, a pressuresensor, and a flow sensor.
 11. The apparatus of claim 10 wherein thecontroller controls the flow based on a measurement obtained from theenvironmental sensor.
 12. The apparatus of claim 11 wherein the conduitstructure is reconfigurable by the controller in a cycle based on atleast one of a time parameter and an environmental parameter from themeasurement obtained from the environmental sensor.
 13. A methodcomprising: transporting warm air in an inflatable non-perforatedblanket having first and second ports in a flow direction; providingconduit to transport the warm air in a conduit structure externally tothe inflatable non-perforated blanket in the flow direction; inflatingthe inflatable non-perforated blanket with the warm air via arecirculating assembly; causing the warm air to flow in the flowdirection internally to the inflatable non-perforated blanket, via therecirculating assembly; and recirculating the warm air through theconduit structure to flow in the flow direction externally to theinflatable non-perforated blanket, via the recirculating assembly;wherein the inflatable non-perforated blanket is adapted to fit asubject body and includes first and second sheets forming first andsecond groups of tubes arranged longitudinally, wherein the first sheetfaces ambient air and is made of a first material, wherein the secondsheet faces the subject body and is made of a second material differentfrom the first, and wherein the conduit structure has a reconfigurableoperational mode to operate in a first mode and a second mode so thatthe flow direction is reversible between a first direction in the firstmode and a second direction in the second mode.
 14. The method of claim13 wherein the first direction is from the first port to the second portand the second direction is from the second port to the first port. 15.The method of claim 14 further comprising controlling the reconfigurableoperational mode.
 16. The method of claim 15 wherein recirculatingcomprises: generating the warm air by heating; and blowing the warm airto the inflatable non-perforated blanket.
 17. The method of claim 15wherein providing conduit comprises controlling flow from the ambientair via an inlet valve.
 18. The method of claim 17 wherein recirculatingcomprises: transporting the warm air to the first port in in the firstdirection and from the first port in the second direction via a firstconduit; transporting the warm air from the second port in the firstdirection and to the second port in the second direction via a secondconduit; and transporting the warm air from the first conduit to therecirculating assembly in the second direction via a first branchconduit, transporting the warm air from the recirculating assembly tothe second conduit in the second direction a second branch conduit,wherein in the first mode the first branch conduit and second branchconduit are closed to allow the warm air to flow from the second conduitto the first conduit through the recirculating assembly, and wherein inthe second mode the first branch conduit and second branch conduit areopen to allow the warm air to flow from the first conduit to the secondconduit through the recirculating assembly.
 19. The method of claim 18wherein controlling flow of the warm air comprises: opening the inletvalve to draw the ambient air to the recirculating assembly and closinga recirculating valve in an initial period; and closing the inlet valveto stop drawing the ambient air to the recirculating assembly after theinitial period and opening the recirculating valve to draw the warm airfrom the first conduit or the second conduit, through a recirculatingconduit and to the recirculating assembly.
 20. The method of claim 17wherein the first material has a first thermal conductivity and thesecond material has a second thermal conductivity higher than the firstthermal conductivity.